Speaking telephone



A. G. BELL. SPEAKING TELEPHONE.

l` N0- 250.704. Patented Dec.13.1881.

FIZ-msm:

fa. e @52M N Firms. mm1@ Lmmgmpngf. wnshmgm. n c.

UNITED STATES PATENT OFFICE.

ALEXANDER Gr. BELL, OF WASHINGTON, DISTRICT OF COLUMBA.

SPEAKING-TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 250,704, dated December 13, 1881.

i Application filed December 2G, 1879.

To all whom it may concern iBe it known that I, ALEXANDER GRAHAM BELL, of Washington, District of Columbia, have invented an Improvement in Speaking- Telephones, of which the following is a specitication. v

This invention relates to telephones having an ear-piece or sound-conveying tube in addition to the ordinary mouth-piece; and it consists in arranging the saidear-pieee or soundconveying tube on the opposite side of the diaphragm or vibrating plate from the mouthpiece. Additional sound-conveyin g tubes communicating with the diaphragmchamber on the same or ou opposite sidcsotthe diaphragm can be used.

In the accompanying drawings, which form a part of this specification, Figure 1 is a plan and Fig. 2 a sectional view of a telephone embodying the invention.

Ais the table to which the instrument is attached.

B B are two blocks of wood held together by screws a, and between which is clamped a diaphragm of thin metal, d, as shown. The blocks B B are, one or both of them, secured tothe table by screws. (Not shown.) Their inner faces are concaved, as shown, to form a chamber, G,within which the diaphragm may vibrate. The front block, B, has an opening for the insertion of the mouth-piece M, and the rear block, B', has an opening for the insertion of one end of an electro-magnet, E, the other end of which is made fast to a bracket, b, screwed to the table, as' shown. The electro-magnet E has a polarized core. Two screw-cups in the table, connected with the electro-magnet by wires, are marked s s.

D D are two trumpet-shaped ear-pieces, counected by flexible tubes with the chamber on either side of the diaphragm, the tubes for that purpose passing through openings or slots in vthe blocks B B.

The operation is as follows: The person about to talk with the telephone holds one ot' the ear-pieces D tohis ear and talks in front of the mouth-piece M in the ordinary manner, pinching the exible tube, however, while he himselt' is talking to prevent the unpleasant sensation of hearing his own voice through the instrument; but when receiving a reply through the same instrument as a receiver he. releases the tube from the extra pressure ot the fingers and hears the return message through the ear-piece at his ear.

It is obvious that conversation can be carried on more readily than when the operator alternately speaks and listens at the mouthpiece.

It is also obvious that where two ear-pieces are attached to the telephone, as shown in the drawings, two persons can receive a message at the same time. might be made to communicate with the chamber within the instrument; but for ordinary purposes one tube provided with an ear-piece in addition to thev mouth-piece is suflicient, and it is immaterial whether the tube communicates with the chamber in front of or in rear ot' the diaphragm.

When more than one ear-piece are attached it may be convenient for the operator to einploy one of them for a mouth-piece.

Having thus fully described my invention and the manner in which the same is or may be carried into effect, what I claim, and desire to secure by Letters Patent, is-

A telephone iu which the receiving and transmitting apertures are placed upon opposite sides ofthe vibrating plate and provided with devices for communicating with the ear and mouth, respectively.

ALEXANDER GRAHAM BELL.

Witnesses:

G.J. HEDRICK, PHILIP MAURO.

So three or more tubesf 

